Gas lift valve

ABSTRACT

A gas lift valve is provided with increased longevity and reliability for preventing backflow. A wide cylindrical sliding member stabilizes axial movement of a valve element in the gas lift valve. A wide spring around the sliding member biases the valve element toward closure during back flow. The spring is physically supported and guided by the sliding member and protected from gas flow injection by the same sliding member. A one-piece poppet version of the valve element provides a consistent closing seal, and the sliding member protects the valve seat and poppet from full force of an injected gas. A dart version of the valve element includes a hexagonal race for movement of the sliding member, which prevents rotational wear of components and provides a straight flow path for the injection gas with no sharp transitions to wear and no sharp angles to erode.

BACKGROUND

Gas lift is a process in which a gas is injected from the annulus of awell into the production tubing of the well, to lower the density of oilbeing recovered, making the fluid easier to lift. “Annulus” as appliedto a well casing refers to the space, lumen, or void around the outsideof a central pipe within a larger pipe, tubing, or casing thatimmediately surrounds the central pipe. An annulus is the space betweenpipes when one pipe is inserted into another pipe. The injected gasaerates to lighten the well fluid for flow to the surface. Gas liftvalves control the flow of gas during either an intermittent orcontinuous-flow gas lift operation. A principle of gas lift operation isdifferential pressure control with a variable orifice size to furtherconstrain the maximum flow rate of gas. By incorporating a hydrostaticpressure chamber that can be charged with different pressures, injectionpressure-operated gas lift valves and unloading valves can be configuredso that an upper valve in the production string opens before a lowervalve opens, even though both valves receive the injection gas from thesame annulus. A gas lift valve is either fully open or fully closed,there is no intermediate valve state. Gas lift valves are oftenretrievable using a kick-off tool in the well. Back check is a criticalcomponent for gas lift valves to prevent the well fluid fromrecirculating back to the annulus of the casing.

SUMMARY

An example gas lift valve includes a first port for receiving a gas froma well annulus, a second port for transferring the gas to a wellproduction tube, a valve seat, a poppet valve element for allowing aone-way flow of the gas past the valve seat and for preventing a backflow of the gas, a sliding barrel attached to the poppet valve elementto maintain a sealing surface of the poppet valve element in alignmentwith a sealing surface of the valve seat, and a spring coiled around theoutside diameter of the sliding barrel to bias the poppet valve elementin a closed position against the valve seat. A one-piece poppet versionof the valve element provides a consistent closing seal. A dart versionof the valve element includes a hexagonal race to prevent rotationalwear of components and a straight flow path for the injection gas withno sharp transitions and angles to wear and erode. An example methodincludes constructing a gas lift valve with a wide cylindrical slidingmember to reliably seat a valve element and biasing the valve elementtoward a closed state with a wide spring around the wide cylindricalsliding member. This summary section is not intended to give a fulldescription of the example gas lift valves. A detailed description withexample embodiments follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example gas lift operation using improved gaslift valves.

FIG. 2 is a diagram of an example gas lift valve assembly.

FIG. 3 is a diagram of a first embodiment of an example gas lift valve.

FIG. 4 is a diagram of a second embodiment of an example gas lift valve.

FIG. 5 is a diagram showing a cross-sectional view of the example gaslift valve of FIG. 4.

FIG. 6 is a flow diagram of an example method of constructing a gas liftvalve.

DETAILED DESCRIPTION

This disclosure describes gas lift valves with improved features. Forcontext, FIG. 1 depicts a gas lift system 100 that includes a productiontubing 140 that extends into a wellbore. For purposes of gas injection,the system 100 includes a gas compressor 120 that is located at thesurface of the well to pressurize gas to be communicated to an annulus150 of the well. To control the communication of gas between the annulus150 and a central passageway 170 of the production tubing 140, thesystem 100 may include several side pocket gas lift mandrels 160(example gas lift mandrels 160 a, 160 b and 160 c). Each of the gas liftmandrels 160 includes an associated gas lift valve 180 (such as examplegas lift valves 180 a, 180 b and 180 c) for establishing one-way fluidcommunication from the annulus 150 to the central passageway 170. Nearthe surface of the well, one or more of the gas lift valves 180 may beunloading valves. An unloading gas lift valve opens when the annuluspressure exceeds the production tubing pressure by a certain threshold,a feature that aids in pressurizing the annulus below the valve beforethe valve opens. Other gas lift valves 180 are located farther below thesurface of the well and may not have an opening pressure threshold.

Each gas lift valve 180 may contain a check valve element that opens toallow fluid flow (gas) from the annulus 150 into the production tubing140 and closes when the fluid would otherwise back flow in the oppositedirection. For example, the production tubing 140 may be pressurized forpurposes of setting a packer, actuating a tool, performing a pressuretest, and so forth. Thus, when the pressure in the production tubing 140exceeds the annulus pressure, the valve element is closed to ideallyform a seal to prevent flow from the tubing 140 to the annulus 150.However, it is possible that this seal may leak, and if leakage doesoccur, well operations that rely on production tubing pressure may notbe able to be completed or performed. The leakage may require anintervention, which is costly, especially for a subsea well.

FIG. 2 shows a gas lift valve assembly 200 in accordance with someembodiments of the example gas lift valves. In general, the gas liftvalve assembly 200 includes an example gas lift valve 180 that includesa valve element (described further below) to control fluid communicationbetween the annulus 150 of the well and the central passageway 170 ofthe production tubing 140. The example gas lift valve 180 resides insidea longitudinal passageway 204 of a mandrel 206. In addition to thelongitudinal passageway 204, the mandrel 206 includes a separatelongitudinal passageway 208 that has a larger cross-section thanpassageway 204, is eccentric to passageway 204, and forms part of theproduction tubing string (140). As depicted in FIG. 2, the longitudinalpassageways 204 and 208 are generally parallel to each other. Themandrel 206 includes at least one radial port 210 to establishcommunication between the longitudinal passageways 204 and 208 and alsoincludes at least one radial port 212 to establish fluid communicationbetween the longitudinal passageway 204 and the annulus 150 of the wellthat surrounds the mandrel 206.

In general, the gas lift valve 180 is configured to control fluidcommunication between the longitudinal passageway 208 and the annulus150 of the well. In this regard, the gas lift valve 180 includes anupper seal 214 and a lower 216 seal (for example, o-ring seals, v-ringseals, or a combination) that circumscribe the outer surface housing ofthe example gas lift valve 180 to form a sealed region that containsradial ports 218 of the example gas lift valve 180 and the radial ports212 of the mandrel 206. One or more lower ports 220 (located near alower end 222 of the longitudinal passageway 204) of the gas lift valve180 are located below the lower seal 216 and are in fluid communicationwith the radial ports 210 near the lower end 222. The longitudinalpassageway 204 is sealed off (not shown) to complete a pocket to receivethe example gas lift valve 180. In this arrangement, the example gaslift valve 180 is positioned to control fluid communication between theradial ports 210 (i.e., the central passageway of the production tubingstring 140) and radial ports 212 (of the mandrel 206, in fluidcommunication with the annulus 150). During operation, the example gaslift valve 180 establishes a one-way communication path from the annulus150 to the central passageway 170 of the production tubing 140. Thus,when enabled, the gas lift valve 180 permits gas flow from the annulus150 to the production tubing 140 and ideally prevents flow in theopposite direction.

The gas lift valve 180 may be installed or removed by a wirelineoperation in the well. Thus, in accordance with some embodiments, theexample gas lift valve assembly 200 may include a latch 224 (locatednear an upper end 226 of the mandrel 206) that may be engaged with awireline tool (not shown) for installing the example gas lift valve 180in the mandrel 206 or removing the example gas lift valve 180 from themandrel 206.

The example gas lift valve assembly 200 may be used in a subterraneanwell or in a subsea well, depending on a particular embodiment.

In an implementation, the example gas lift valve 180 has a generaldesign that is depicted in FIG. 3. Radial ports 218 of the example gaslift valve 180 may be formed in a tubular housing 302 of the example gaslift valve 180. The tubular housing 302 may be connected to an upperconcentric housing section 304 of the gas lift valve 180 that extends tothe latch 224 (not shown in FIG. 3).

The housing 302 includes an interior space 305 for receiving gas thatflows in from the radial ports 218. Injection gas that enters the radialports 218 flows into the interior space 305 and through an orifice 306,which may be connected to the lower end of the housing 70. The orifice306 may by cylindrical, square-edged, or streamlined for ventureeffects, for example. The housing around the orifice 306 may bepartially circumscribed by the lower end of the housing 302 and may besealed to the housing 302 with one or more seals 308, such as o-rings,for example. The housing of the orifice 306 may extend inside an upperend of a lower housing 310 that is concentric with the housing 302 andextends further downhole. The housings 310 and 302 may be sealedtogether via one or more seals 312, such as o-rings. As also depicted inFIG. 3, the lower seal 216 (formed from one or more v-type seals,o-rings, etc.) may circumscribe the outer surface of the housing 310 insome embodiments. The orifice 306 is in communication with a lowerpassageway 314 that extends through the housing 310.

Poppet Back Check Valve Embodiment

In an implementation, the lower end of the housing 310 forms a valveseat 316, a seat that is opened and closed (for purposes of controllingthe one-way flow through the gas lift valve 180) via a valve element 322of a check valve assembly 318. The check valve assembly 318 may bespring-loaded using, for example, spring 320 in a guided springassembly. The check valve assembly 318 may be anchored or secured via asocket-type connection to a movable, sliding, hollow cylindrical member,such as a piston or barrel 324 surrounded by the inside diameter ofcoils of the spring 320. The check valve assembly 318 moves as a unitdepending on the injected gas pressure, allowing pressurized gas to flowthrough the valve end of the barrel 324 in a controlled manner.

In an implementation, a poppet-shaped version of the valve element 322(“poppet valve element” 322) allows gas flow, or closes off gas flow asthe case may be, controlling fluid communication through the valve seat316. The check valve assembly 318 exerts an “upward” bias force (towardsthe surface, i.e., toward closure of the example gas lift valve 180against back pressure) on the valve element 322 for biasing the valveelement 322 to close off fluid communication through the valve seat 316.

The particular mushroom-like geometry of a poppet-shaped disk, when usedas the valve element 322, provides a concerted valve closure all the wayaround the sealing perimeter of the poppet valve element 322 when thepoppet valve element 322 shuts during pressure scenarios that wouldcause backflow. In an implementation, a one-piece poppet valve element322 ensures alignment of the seal surface when it closes.

Besides this consistent evenness of the closing seal due to the poppetgeometry, the poppet valve element 322 also provides reliability in theseal that is created between the poppet valve element 322 and the valveseat 316. The poppet-shaped valve element 322, as guided by the pistonor barrel 324 that supports the spring 320, moves smoothly and reliablyin one axial direction for opening and closing. The relatively largebore of the barrel 412 located just inside the coils of the spring 406provides strength and smoothness to the axial movement of the dart valveelement 404, and removes unnecessary play, as compared with conventionalback check valves that use a spindly support member for movement of aconventional valve element.

In an implementation, the cross-sectional diameter of the barrel 324 maybe substantially the same diameter as that of the poppet valve element322 to maintain a sealing surface of the poppet valve element 322 ingood or perfect parallel-planar alignment with a sealing surface of thevalve seat 316. Thus, the geometry of the check valve assembly 318affords the poppet valve element 322 reliable and smooth movement, sothat the poppet valve element 322 makes a consistent leak-proof seal.Thus, the poppet valve element 322 snaps shut against the valve seat 316in consistent alignment making a quick and reliable seal when thepressure in the production tubing 140 becomes greater than the pressurein the annulus 150.

When, however, the annulus pressure is sufficient (relative to theproduction tubing pressure) to exert a force on the poppet valve element322 to overcome the bias of the spring 320, then the poppet valveelement 322 retracts (opens downward) to permit gas fluid to flow fromthe annulus 150 into the production tubing 140 to effect gas lift.

The lower end of the lower housing 310 may be sealed via an o-ring 328for example, to a nose housing or end housing 326 that extends furtherdownward toward the lower port(s) 220 of the example gas lift valve 180.An interior space 330 inside the end housing 326 is in communicationwith the production tubing side (140 and 170) of the example gas liftvalve 180 and receives the injected gas via the annulus 150 that opensthe check valve assembly 318 and flows through the valve seat 316.

An example gas lift valve 180 that includes the poppet valve element 322provides several other advantages. A wide spring 320 can be used and theinside diameter (ID) of the spring 320 can be disposed around and guidedby the piston or barrel 324, as shown. This arrangement provides steadyand reliable movement of the poppet valve element 322 as compared withconventional spring-loaded valve elements that either rely on anunsupported spring or rely on a narrow spring that imparts too much playin the side-to-side movement of a conventional valve element. In FIG. 3,the spring 320 is also protected from the flow stream, adding tolongevity and reliable function of the spring 320. The design andgeometry of the example gas lift valve 180 also avoids direct high speedflow past the sealing surface, which can provide a valve closure forpreventing backflow that is more sensitive to smaller backflowpressures. In an implementation, the movement of the open poppet valveelement 322 is stopped by the poppet valve element 322 itself contactingthe nose housing or end housing 326 of the example gas lift valve 180,as compared with conventional techniques of having movement limited byother components attached to a valve element, which could cause thevalve element to stick at an open position.

Ideally, fluid cannot flow from the production tubing side of the checkvalve assembly 318 to the annulus side, because of the poppet valveelement 322 closing and making a seal against the valve seat 316.

Hex Dart Back Check Valve Embodiment

FIG. 4 shows an example hex dart gas lift valve 402, which includes anexample valve race 502 (FIG. 5) that has a hexagonal cross-section, andincludes a dart style back check valve element 404 (“dart valve element”404). This example embodiment of a gas lift valve 402 provides severaladvantages, including a gas flow path that is relatively free from sharpangular transitions, to reduce wear and increase longevity. Thehexagonal geometry of the hex dart gas lift valve 402 counteractserosion at sharp corners, especially when some impurities or abrasivesalso flow through the valve components with the injected gas. The hexdart gas lift valve 402 uses a spring 406 that is fully guided on itsinside diameter (ID) for stability. The hex-shaped race 502 (FIG. 5) ofthe hex dart gas lift valve 402 can also prevent rotation of the dartvalve element 404 and connected components (and thus prevent valvesticking) caused by high velocity gas flow.

In FIG. 4, a lower housing 408 of the example gas lift valve 402provides the structure for a valve seat 410. The valve seat 410 opens orcloses for controlling one-way flow through the example gas lift valve402 via the dart valve element 404. A piston, hollow cylindrical member,or barrel 412 may be spring-loaded using, for example, spring 406 aroundthe outside diameter of the barrel 412 in a guided spring assembly. Thedart valve element 404 may be anchored or secured via a socket-typeconnection 414 to the piston or barrel 412 that is surrounded by theinside diameter of the spring 406.

The dart valve element 404, connector 414, and barrel 412 move as a unitto open against the expansive bias of the spring 406, which is set tokeep the valve closed, opening when injected gas pressure overcomes theforce of the spring 406. Orifice openings near the connector 414 mayallow control of the amount of pressurized gas that can flow through thevalve seat 410 at a given time, thereby adding control and sensitivityto the valve.

The dart valve element 404 is guided in its movement by the barrel 412that stabilizes and guides the spring 406. The relatively large bore ofthe barrel 412 located just inside the coils of the spring 406 providesstrength and smoothness to the axial movement of the dart valve element404, and removes unnecessary play, as compared with conventional backcheck valves that use a spindly support member for movement of aconventional valve element. In an implementation, the diameter of thebarrel 412 may be substantially the same diameter as that of the dartvalve element 404. The relatively wide spring 406 and the geometry ofthe hex race 502 and wide barrel 412 member affords the dart valveelement 404 reliable and smooth movement, so that the dart valve element404 makes a consistent leak-proof seal. The dart valve element 404 shutsagainst the valve seat 410 in consistent alignment making a reliableseal when the pressure in the production tubing 140 becomes greater thanthe pressure in the annulus 150, resulting in a potential back flowcondition.

When the annulus pressure is sufficient (relative to the productiontubing pressure) to exert a force on the dart valve element 404 toovercome the bias of the spring 406, then the dart valve element 404 ispushed back (opens downward) to permit gas fluid to flow from theannulus 150 into the production tubing 140 to effect gas lift.

The lower end of the lower housing 408 may be sealed via an o-ring 416for example, to a nose housing or end housing 418 that extends furtherdownward toward the lower port(s) 420 of the example hex dart gas liftvalve 402. An interior space 422 inside the end housing 418 is incommunication with the production tubing side (140 and 170) of theexample hex dart gas lift valve 402 and receives the injected gas viathe annulus 150 that opens the dart valve element 404 and flows throughthe valve seat 410.

FIG. 5 shows an example cross-section of a hexagonal race 502 of the hexdart gas lift valve 402, as viewed from the plane in FIG. 4 designated(in 2D) by line C-C. Depending on implementation, part of the barrel 412may be hexagonal and ride in the hexagonal race 502, or in someimplementations the entire barrel 412 may have a hexagonal outsidesliding surface, or in still other implementations, the entire valveelement assembly, including the dart valve element 404 may havehexagonal outer presentations. The hexagonal race 502 prevents rotationof the dart valve element 404 and associated components, and thusprevents extra surface wear and potential valve sticking that can becaused by high velocity gas flow.

EXAMPLE METHOD

FIG. 6 is a flow diagram of an example method 600 of constructing a gaslift valve. In the flow diagram the individual operations are shown asblocks.

At block 602, a gas lift valve is constructed to include a widecylindrical sliding member to reliably seat a valve element. The widecylindrical sliding member, or barrel, is attached to the valve element.Because the barrel moves within a large bore, the barrel has very stablemovement in an axial direction with very little play in other movementdirections. This assures a strong and correctly aligned seal matingbetween the valve element and the valve seat.

At block 604, the valve element is biased toward a closed state with awide spring around the wide cylindrical sliding member. The wide springis both supported by the wide cylindrical sliding member and protectedfrom the gas being injected by the wide cylindrical sliding member.

The wide cylindrical sliding member and the spring may have across-sectional diameter substantially the same as a largest diameter ofthe valve element in order to maintain a sealing interface of the valveelement and a valve seat in a parallel-planar alignment with each otherwith very little deviation to a side. The wide cylindrical slidingmember can also protect the valve element and a valve seat from fullforce of a gas injection flow.

A poppet valve element connected to the wide cylindrical sliding memberreliably closes the gas lift valve during a back flow condition.Alternatively, a dart valve element in the gas lift valve prevents aback flow condition and when used with a hexagonal race or bore for thewide cylindrical sliding member, rotational wear of the valve componentscaused by a high velocity gas flow can be prevented. The hexagonal racealso provides a flow path for the injected gas that is free from sharpangular transitions counteracts erosion at sharp corners.

Conclusion

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from the subject matter. Accordingly, all such modificationsare intended to be included within the scope of this disclosure asdefined in the following claims. In the claims, means-plus-functionclauses are intended to cover the structures described herein asperforming the recited function and not only structural equivalents, butalso equivalent structures. It is the express intention of the applicantnot to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any ofthe claims herein, except for those in which the claim expressly usesthe words ‘means for’ together with an associated function.

1. A gas lift valve, comprising: a first port for receiving a gas from awell annulus; a second port for transferring the gas to a wellproduction tube; a valve seat; a poppet valve element for allowing aone-way flow of the gas past the valve seat and for preventing a backflow of the gas; a sliding barrel attached to the poppet valve elementto maintain a sealing surface of the poppet valve element in alignmentwith a sealing surface of the valve seat; and a spring coiled around theoutside diameter of the sliding barrel to bias the poppet valve elementin a closed position against the valve seat.
 2. The gas lift valve ofclaim 1, wherein the sliding barrel and the spring have a widecross-sectional diameter substantially the same as a diameter of thepoppet valve element to maintain a sealing interface of the poppet valveelement and the valve seat in parallel-planar alignment with each other.3. The gas lift valve of claim 1, wherein the poppet valve elementcomprises a one-piece member for alignment of a sealing surface of thepoppet valve element with a sealing surface of the valve seat.
 4. Thegas lift valve of claim 1, wherein the spring is protected from a mainflow of the gas by the barrel.
 5. The gas lift valve of claim 1, whereina sealing interface between the poppet valve element and the valve seatis protected from a direct high speed flow of the gas by at least onevalve component.
 6. The gas lift valve of claim 1, wherein a maximumopen state of the poppet valve element is determined by the poppet valveelement contacting an end housing of the gas lift valve.
 7. A gas liftvalve, comprising: a first port for receiving a gas from a well annulus;a second port for transferring the gas to a well production tube; avalve seat; a dart valve element for allowing a one-way flow of the gaspast the valve seat and for preventing a back flow of the gas; a slidingbarrel attached to the dart valve element to maintain a sealing surfaceof the dart valve element in alignment with a sealing surface of thevalve seat; a spring coiled around the outside perimeter of the slidingbarrel to bias the poppet valve element in a closed position against thevalve seat; and a race of hexagonal cross-section for a movement of thesliding barrel.
 8. The gas lift valve of claim 7, further comprising aflow path for gas substantially free from sharp angular transitions. 9.The gas lift valve of claim 7, wherein a hex dart configurationcounteracts erosion at sharp corners.
 10. The gas lift valve of claim 7,wherein the spring is fully-guided on an inside diameter (ID) of thespring for stability.
 11. The gas lift valve of claim 7, wherein a hexdart configuration prevents a rotation of a valve component caused byhigh velocity gas flow.
 12. The gas lift valve of claim 7, wherein thesliding barrel and the spring have a wide cross-sectional diametersubstantially the same as a diameter of the dart valve element tomaintain a sealing interface of the dart valve element and the valveseat in parallel-planar alignment with each other.
 13. The gas liftvalve of claim 7, wherein the spring is protected from a main flow ofthe gas by the barrel.
 14. The gas lift valve of claim 7, wherein asealing interface between the dart valve element and the valve seat isprotected from a direct high speed flow of the gas by at least one valvecomponent.
 15. A method, comprising: constructing a gas lift valve witha wide cylindrical sliding member to reliably seat a valve element; andbiasing the valve element toward a closed state with a wide springaround the wide cylindrical sliding member.
 16. The method of claim 15,wherein the wide cylindrical sliding member and the spring have across-sectional diameter substantially the same as a largest diameter ofthe valve element to maintain a sealing interface of the valve elementand a valve seat in a parallel-planar alignment with each other; andwherein the wide cylindrical sliding member protects the valve elementand a valve seat from a full force of a gas injection flow.
 17. Themethod of claim 15, wherein the spring is protected from a main flow ofan injection gas by the wise cylindrical sliding member.
 18. The methodof claim 15, further comprising attaching a one-piece poppet-shapedvalve element to the wide cylindrical sliding member to reliably closethe gas lift valve during a back flow condition.
 19. The method of claim15, further comprising: incorporating a dart valve element in the gaslift valve to prevent a back flow condition; and incorporating ahexagonal race for the wide cylindrical sliding member in the gas liftvalve to prevent a rotation of the valve components caused by a highvelocity gas flow.
 20. The method of claim 19, wherein the hexagonalrace provides a flow path for a gas substantially free from sharpangular transitions; and wherein the hexagonal race counteracts erosionat sharp corners.